The pyrite films with the thickness of 70-600 nm were prepared by annealing the iron films with the thickness of 25-150 nm at 673 K. The structural, optical and electrical characteristics were investigated and the effect of film thickness on film properties was discussed. The pyrite films with different thickness have the optical absorption edges changed in the 0.93-1.0-eV range. With the increase in film thickness, electrical resistivity tends to increase and carrier concentration tends to decrease. It is speculated that surface defects in thinner films could play a more important role in the effect on film properties whereas grain boundary defects in thicker films could play a more important role in the effect on film properties. (c) 2004 Elsevier B.V. All rights reserved.